On March 8, the young South Philadelphia resident will donate bone marrow to help save the lives of his twin 4-month-old brothers, Santino and Giovanni, who suffer from a rare immune disease, WTXF reported. The procedure will take place at the Children’s Hospital of Philadelphia, Philly.com reported.

The twins were diagnosed with chronic granulomatous disease, which affects one in 500,000 persons each year, WTXF reported. The family’s oldest child, Dominick, also was born with the disease.

Pownall said she was impressed by Michael Jr.’s strength.

“He goes to the doctor when he gets the labs for the pre-testing, and he says, ‘Look how strong I am,’ and he gives them willingly his arm to get blood work. The nurses are amazed,” Pownall told WTXF. “They're like, ‘I cannot believe how brave he is,’ and he really is. It gives me chills.”

The family started a GoFundMe page to help with medical costs, WTXF reported.